Improved WRF-Chem Representation of VOC Chemistry from VCP and Cooking Emissions

Volatile organic compound (VOC) reactions with hydroxyl radicals (OH) and nitrogen oxides (NOx) fuel the production of air pollutants like ozone and particulate matter (PM). The representation of VOC chemistry remains challenging in reduced chemical mechanisms due to its complexity in speciation and reactions. We aim to develop a chemical mechanism that is compatible with WRF-Chem that better represent VOC chemistry in urban areas such as Los Angeles. We show that this chemical mechanism, RACM2B-VCP, is based on RACM2_Berkeley2 mechanism and includes more complex oxygenated VOC chemistry to address the impact of VCP and cooking emissions. We then incorporate the TUV photolysis scheme, a more complex SOA_VBS scheme, and aerosol uptake reactions to better represent photolysis, aerosol, and ozone, respectively. We also add new species, D4 siloxane, D5 siloxane, p-Dichlorobenzene and PCBTF as VCP tracers; nonanal and octanal as cooking emission tracers. We evaluate how well this RACM2B-VCP mechanism simulates VOC chemistry, ozone and PM2.5 in WRF-Chem by comparing against a series of observations, including airborne measurements from the RECAP-CA field campaign, mobile and in-situ measurements from the SUNVEX field campaign as well as AQS networks in summer 2021 over the LA Basin. We then discuss how ozone changes due to each VOC emission sector and provide insights on VOC emission control strategy for ozone regulations in both current and future scenarios.